Improvement in rotary-disk measures



E. V. LAWRENCE.

Rotary Measure.

No. 37,002. Patented Nov. 25, 1862 mine-10cm wfiafmw m K. PFIERS.Phulo-Likhognplwr. Wllllinglon. D. Q

1y 1 Ir UNITED STATES PATENT Orricno lMPROVEMENT IN ROTARY-DISKMEASURES.

Specification forming part of Letters Patent No. 37,002, dated November25, 1862.

To all whom/it may concern.-

Be it known that I, E. V. Lawnnncn, of Brooklyn, in the county of Kingsand State of New York, have invented a new and Improved Itotary-DiskMeasure; and I do hereby declare that the following is a full, clear,and exact description of the same, reference being had to theaccompanying drawings, making a part of this specification, in which-Figure 1 is a face view of my invention. Fig. 2 is a plan or top view ofthe same.

Similar letters of reference in both views indicate corresponding parts.

The object of this invention is an improvement in that class of measuresin which the perimeter of a rotary disk is used for the purpose ofdetermining the linear dimensions of plane or curved surfaces.

The invention consists in the combination, with the rotary disk, andwith the ecg-wheeis which transmit the motion of said disk to theindex-hands, of a case of known width,which incloses the whole measure,with the exception of a small portion of the disk, and which is providedwith a pointer in such a manner that the disk can be started accuratelyfrom any desired point, and at the same time the instrument is inclosedin a small compass and can conveniently be carried in the pocket.

It consists, further, in the application to the periphery of the rotarydisk of a strip of india-rubber or leather, for the purpose ofpreventing the disk from slipping while being carried over the surfaceto be measured.

It consists, further, in the application to the case which incloses themeasuring-disk and wheels of a pointed radius-bar, in combination with asuitable scale marked on the dial-plate of the case in such a mannerthat by inserting the point of the radius-bar in the point of the angleand carrying the disk over the are measuring said angle the number ofdegrees contained in the arc, and also its length, may be determinedwith ease and facility.

It consists, finally, in the arrangement of a compass, inserted intoIthehandle,which serves to carry the disk over the surface to be meas uredin such a manner that the direction in which the disk moves can beobserved at every point.

To enable those skilled-in the art to make and use my invention, I willproceed to describe it with reference to the drawings.

A represents a disk, made of sheet metal or any other suitable material,and secured to an arbor, a, which has its bearings in the front and backplates of the case B. The perimeter of this disk is equal to six or anyother known number of inches, and said disk, which rotates freely on itsarbor, protrudes below thelower edge of the case, so that on bringingthe latter down upon the surface to be measured in an upright positionthe edge of the disk comes in contact with said surface, and if the caseis then moved over the surface the disk rotates. The case is providedwith a pointer, a, so

that the disk can be started accurately from 7 any desired point. Thewidth of the case is exactly two (or any other known number of) inches,and the distance of the pointer is equal to one-half the width of thecase from either edge, so that in measuring a line which terminates in acorner, by adding one inch, or half the width of the case, to the numberindicated by the instrument, the correct measurement is obtained. Therotary motion of the disk' is transmitted to the index hands O D bymeans of wheels b b c 0 and pinions d d. The wheels I) b, which impartmotion to the index 0, are so proportioned in relation to the perimeterof the disk that one complete revolution of said index indicates exactlyone foot or twelve inches traversed by the disk, and the pinions d d andwheels 0 c, which impart motion to the index D, are of such a sizerelatively, when compared with the perimeter of the disk, that onerevolution of the first index produces onesixtieth part of a revolutionof the second index. Scales e e' are engraved on or otherwise attachedto the front plate of the case, one for the index 0, to indicate thenumber of inches, and one for the index D, to indicate the number offeet traversed by the disk A.

In applying the disk A to a smooth surface, if the metallic edge of thesame would be allowed to come in immediate contact with said surface itwould be liable to slip and an inaccurate result would betheconsequence. To obviate this diffieulty, I have applied to the edgeof the disk a thin strip, f, of india-rubber, leather, or other suitablematerial by inserting the same in a groove turned in said edge in such amanner thatit projects very slightly beyond it, and that the diameter ofthe disk' is not materially changed, and at the same time a slipping ofthe same is prevented.

E is a radius-bar provided with a point, 9, at one end, and arranged atthe other end with a screw-thread screwing into a socket in the backplate of the case. This radius-bar is intended to measure angles; andthis object is effected in the following manner: The point 9 is insertedin the point of the angle, and the disk A is now carried over the are,which measures said angle. If the length of the radius-bar is known theactual length of Y arcs of smaller or larger diameters can easily befound by calculation. The number of degrees of the arcs to be measuredare determined by a scale, e on the dial-plate. This scale shows thenumber of degrees from 0 to 90; but it will be easily understood that bya suitable change in the wheels and pinions the scale 6* might be madeto indicate minutes and parts of minutes, and in the same manner thescale 6 might be made to indicate fractional parts of inches, if itshould be desirable; or the wheels might be so arranged that by means ofthe disk-measure a line of certain known length could be divided in anydesired number of parts. The handle F of the case is turned out in theshape of a small cup or cylindrical box to receive a paper card markedwith the points of direction and fixed to a magnetic needle, thusconstituting a regular compass, whereby the direction can be determinedin which the disk moves. This compass attachment is of particular valuein laying out maps or in surveying or in determining the course of avessel on sea.

In its simplest construction, without the compass and radius-bar, myinstrument will be of particular value for mechanics or draftsmen forthe purpose of determining the dimensions of plain or curved surfaces.With the radius-bar and compass it will be used with advantage bysurveyors and other persons in laying out maps or making trigonometricalcalculations, and it may be attached to theodolites' or otherinstrumentsfor measuring with a graduated scale, for the purpose of observing withperfect accuracy measurements of straight or curved lines.

Having thus fully described my invention, what I claim as new, anddesire to secure by Letters Patent, is

1. The arrangement of the cylindrical case B with its pointer a, incombination with the rotary disk A, wheels I) b c c d d, and indexhands0 D, all constructed and operating in the manner and for the purposeshown and described.

2. The application of a strip, f, of indiarubber or other suitablematerial, to the edge of the rotary disk A, when said disk is used asand for the purpose set forth.

3. The arrangement of the radius-bar E with point in combination withthe case B, carrying the measuring-disk wheels and indices, allconstructed and operating substantially as and for the purposedescribed.

4:. The use of a compass, in combination with the handle F of the caseB, as and for the purpose specified. EDGAR V. LAWRENCE. WVitnesses:

TIMOTHY SHINE, M. S. PARTRIDGE.

